Adhesively bonded radiator assembly

ABSTRACT

A radiator assembly ( 10 ), including an end tank ( 12 ) having a first mating surface ( 14 ) and a heat exchanger ( 16 ) having a second mating surface ( 18 ). The heat exchanger ( 16 ) is adhesively bonded to the end tank ( 12 ) with an adhesive (22).

TECHNICAL FIELD

[0001] The present invention relates to adhesively bonded engine component assemblies and more particularly to adhesively bonded radiator assemblies. The invention also relates to radiator assemblies employing a cure-on-demand adhesive.

BACKGROUND OF THE INVENTION

[0002] Historically, fabrication techniques for the manufacture of automotive engine radiators have involved the fabrication of separate metal components (e.g., the heat exchanger and corresponding end tanks) and the joinder of the components using expensive brazing techniques (e.g., for aluminum or copper assemblies) or crimped tangs associated with one or more of the components about substantially the entirety of the assembly periphery. This tends to be labor intensive and the scrap rate tends to be high in view of the potential for misalignment of the components, the severity of operations often leading to broken tangs or other factors contributing to a poor seal.

[0003] Moreover, the nature of such assemblies has required that rectangular heat exchangers be employed, thereby providing generally flat upper and lower mounting surfaces upon which the end tanks are attached. In view of the ever growing need for lightening vehicles and maximizing usage of space in the vehicle engine compartment, it has become increasingly desirable to design radiator assemblies having unconventional, non-rectangular configurations. The need for assembling end tanks to a non-rectangular heat exchanger, however, has not been met, because there has been no practical manner for securing the components together.

[0004] Accordingly, there is a need to provide a method of manufacture and resulting assembly, pursuant to which multiple components of a radiator assembly are joined together with an adhesive bond. There is a further need for respective components to be attached to each other in the optional absence of fasteners, a gasket or both. There is still a further need for a high integrity joint be achieved opposing mating surfaces that are non planar, thereby enabling intricate plastic component shapes (with or without additional integrated components) to be molded by conventional molding processes.

SUMMARY OF THE INVENTION

[0005] The present invention meets the above needs and others by providing an automotive engine radiator assembly including at least one end tank having a first mating surface, and a heat exchanger having a second mating surface. A layer of adhesive is provided between the end tank and the heat exchanger in contact with the respective mating surfaces for joining the end tank and heat exchanger to define a radiator assembly.

BRIEF DESCRIPTION OF THE DRAWINGS

[0006]FIG. 1 is an exploded perspective view of a radiator assembly in accordance with the present invention.

[0007]FIG. 2 is a sectional view of joints formed in accordance with the present invention.

[0008]FIGS. 3a-3 b are sectional views of examples of integrated mechanical attachments in the components of the assembly of the present invention.

[0009]FIGS. 4a-4 c are views of alternate radiator assemblies in accordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0010] Referring to FIGS. 1 and 2 there is shown a radiator assembly 10 of the present invention including a first end tank 12 having a first mating surface 14. A heat exchanger 16 having a second mating surface 18 (e.g., shown on an end plate in FIG. 1) and a third mating surface 20. The first end tank 12 is bonded to the heat exchanger 16 with a first intermediate layer of adhesive 22. In a particularly preferred embodiment, a second end tank 24 having a fourth mating surface 26 is bonded with a second intermediate layer of adhesive 28 to the heat exchanger 16. Any or all of the first, second, third or fourth mating surfaces can include one or more additional coatings, layers or components. Thus, it is contemplated that the mating surfaces of any of the components may not necessarily be integrally formed on the components.

[0011] Optionally, either or both of the end tanks, the heat exchanger, or all of them, has a structure for facilitating jointer or location of the components relative to each other. Referring more specifically to FIGS. 2 and 3a-3 b (where like parts are denoted by like reference numerals), there are shown examples of different structures. Typically, a first mating structure 30 associated with one component (e.g., an end tank) will engage a second mating structure 32 associated with the heat exchanger. In like manner, the first and second mating structures 30 and 32 can be interchanged between the end tank and heat exchanger. Such engagement can be about the periphery of a component, on an interior portion (not shown) or both.

[0012] In one embodiment, shown in FIG. 3a, a mating joint 34 results from a flange 36 on the heat exchanger penetrating a peripheral wall defining a groove 38 formed on the end tank, wherein adhesive is placed in the groove 38. In another embodiment, in FIG. 3b, adhesive is applied to a peripheral wall 40 on the heat exchanger and the mating surface 14 of the end tank 12. As indicated the above structural features could be interchanged as between the end tank and the heat exchanger. Combinations of the above types of joints are also contemplated as possible within a single assembly. Further, as desired, any suitable coating structure may be employed. For instance, a friction fit, an interference fit or some other interlock fit may be used. Examples of suitable joints include butt joints, lap joints, tongue in groove joint or the like. Further examples are illustrated in commonly owned, co-pending U.S. application Ser. No. ______ (filed contemporaneously herewith; entitled “Adhesively Bonded Engine Intake Manifold Assembly”). Other suitable structures or surface treatments may be employed for providing an increase in the amount of surface area of the mating surfaces of the joint, or the overlap between the respect mating surfaces of the components. Further, as will be appreciated from FIG. 3a, optionally, a tang or other like structure may be formed (e.g., on mating structure 32) for assisting in achieving a snap fit or for providing an audible locator for facilitating assembly. It should also be appreciated that the above structures may be suitably interchanged between components. For example, the flanges may be formed on a heat exchanger (e.g., at an end plate) or on a heat exchanger end tank and complementary mating structure formed on the other.

[0013] The adhesive preferably is provided over at least a portion of the surfaces to be joined, and preferably sufficiently about the periphery so that there are no appreciable gaps that result between joined components. In one embodiment, a bead of adhesive is placed (e.g., by pumping) on the respective mating surface of at least one of the components and the opposing mating surface is brought into contact with it. The assembly is then cured. In another embodiment, the adhesive is precoated (e.g., by spraying, dipping, brushing, swabbing, or the like) on one or both of the mating surfaces of the respective components and then the components are joined and cured. Any other suitable joining technique may likewise be employed. Preferably the amount of adhesive employed is sufficient to achieve the desired performance characteristics of the assembly. Such amount will vary from application to application.

[0014] In one embodiment the invention encompasses having disposed on the mating surfaces of the respective components a continuous bead or film of adhesive. As used herein continuous bead or film of adhesive means a bead or film of adhesive that is disposed around the periphery of the mating surface and the end of the adhesive bead or film connects with the beginning of the adhesive bead or film. The continuous bead or film of adhesive upon cure is capable all of forming an air and liquid tight seal between the components. This function allows the adhesive bead or film to replace gaskets as the sealing means. The adhesive may be applied to the radiator components in the immediate vicinity of the location where the components are to be contacted with each other or it may be applied in a location remote from where or when the components are to be contacted. Remote as used herein refers can refer to one or both of time and location. In the embodiment where the adhesive is applied to one or more of the components remote from the place wherein the components are joined together a cure-on-demand adhesive is used.

[0015] In a preferred embodiment of the present invention, the end tanks, heat exchanger or each of them is fabricated from a plastic material, i.e., a thermoset material, a thermoplastic material, or a mixture thereof. Among preferred high-performance thermoplastic materials are polybutylene terephthalate, polyetherimides, polyphenylene ether/polyamide resins, polyether sulfone resins, polyether ether ketone resins, liquid crystal polymers, polyarylsulfone resins, polyamideimide resins, polyphthalimide resins, nylon 6, 6, polyamide resins, syndiotactic polystyrene, and blends thereof. In a particular preferred embodiment, the material is a thermoplastic selected from polyamides, polystyrenes, polyolefins, polycarbonates, or mixtures thereof. More preferably, the material is selected from polyamides (e.g., nylon 6,6), polystyrenes or mixtures thereof. In one preferred embodiment, the material is a blend of polyamides and syndiotactic polystyrenes, and more preferably a blend of nylon 6,6 and syndiotactic polystyrene. Among useful thermoset materials are epoxy resins.

[0016] The plastics used for preparing the components typically will also include other ingredients, such as reinforcements, property modifiers (e.g., impact modifiers, flame retardants, UV protectants or the like) or other suitable fillers (e.g., chopped glass, mineral, talc, calcium carbonate, or the like). For instance, in one embodiment, the plastic is glass filled in an amount of about 10 to about 50 volume percent and more preferably about 35 volume percent. Preferably, the material selected exhibits a tensile strength of at least about 175 MPa and more preferably at least about 225 MPa, and an elongation of about 1 to about 10%, and more preferably about 3 to about 5%. The material is also thermal resistant and will withstand without degradation temperatures of at least about 135° C. (about 275° F.) and more preferably 177° C. (350° F.) for at least about 144 hours and more preferably 168 hours.

[0017] Of course, one or more of the components might be a metal (e.g., cast iron, steel, magnesium, aluminum, titanium or the like), a composite, a ceramic (e.g., a carbide, a nitride, a boronitride, or the like), or some other material. The plastic components of the assembly are preferably injection molded using conventional techniques and processing conditions. Alternatively, they may be prepared in another suitable manner, such as by compression molding, thermoforming, blow molding or the like.

[0018] Either or both of the component materials or the adhesive may be suitably treated (uniformly or locally) as desired to improve corrosion resistance, oxidation resistance, thermal resistance, or another characteristic of the final product. For instance, they might be admixed, impregnated or coated with suitable additives for achieving a desired property. In some instances, bond strengths might be enhanced by further contacting the adhesive with a suitable primer.

[0019] The adhesive of the present invention is a structural adhesive and more preferably is a curable on demand material. Any adhesive that after cure can withstand the conditions of use of an engine (e.g., for an automotive vehicle) can be used. Preferably such adhesive does not decompose or delaminate at temperatures of up to about 138° C. (280° F.), more preferably up to about 143° C. (290° F.), even more preferably up to about 160° C. (320° F.) and most preferably up to about 191° C. (375° F.).

[0020] Furthermore, the adhesive is able to withstand exposure to hydrocarbon materials, calcium chloride, brake fluid, glycol coolants, windshield washer solvents and the like, at the above-mentioned temperatures and the pressures to which the internal combustion engine reaches internally. In an optional embodiment, the adhesive is able to bond to other engine components, which may be metallic, ceramic, composite, plastic, or the like. The adhesive used may be curable via a variety of known mechanisms including heat cure, infrared cure, ultraviolet cure, chemical cure, radio frequency cure, solvent loss and moisture cure.

[0021] In another embodiment the adhesive is a cure-on-demand adhesive which requires a separate operation to cause the adhesive to begin to cure. In one embodiment this is achieved by using an encapsulated curing agent which is ruptured during assembly. In another embodiment this is achieved by removing a protective coating to expose the adhesive to ambient conditions. Cure can be initiated by exposing the adhesive to heat, infrared or ultraviolet light sources, or to shearing forces and the like.

[0022] While other adhesive families are contemplated as well (e.g., urethanes, acrylics, silanes, or the like), preferably the adhesive is a high temperature epoxy resin, a polyimide, a hi-bred polyimide/epoxy resin adhesive or an epoxy novolac/nitrile rubber adhesive. Preferred adhesives are the high temperature epoxy resin adhesives. High temperature epoxy resin adhesive means an adhesive wherein the primary component is an epoxy resin which when cured can withstand exposure to the temperatures mentioned above without decomposing or delaminating from the substrate.

[0023] In a particularly preferred embodiment, the adhesive is a mineral filled catalyzed adhesive that includes one or more regular or modified epoxy components, a suitable curing agent and a suitable thixotropic agent for maintaining a room temperature Brookfield viscosity (in uncured state) on the order of about 500 cps.

[0024] It should be recognized that the use of the term adhesive herein is not intended to foreclose primers or other bonding agents from the scope of the present invention.

[0025] The present invention offers considerable design flexibility. Though mating surfaces can be planar, they need not be. In a preferred embodiment, either or both of the mating surfaces is generally non planar (e.g., contoured, stepped, corrugated, or the like). The employment of molded plastic components also enables the formation of intricately shaped structures. In this regard, the radiator assembly can have molded or otherwise fabricated in or on one of its surfaces one or more components such as brackets, connectors, cable guides, hose guides, harnesses, clips or the like. Further, conduits, ports or other like passages can be cored or machined into a molded component to enable integration of multiple components into the radiator assembly.

[0026] As will be appreciated by the skilled artisan, among the many advantages of the present invention are that assemblies can be made that are substantially free of folding tangs, a sealing gasket, mechanical fasteners or all of these. However, the scope of the present invention does not foreclose the use of folding tangs, gaskets or fasteners. Indeed, it is contemplated that a gasket might be made from (e.g., by die cutting a gasket) from the adhesive or incorporate as a component thereof (e.g. as an impregnant or coating), the adhesive of the present invention. The resulting structure seals much like a gasket would, but also exhibits the desirable mechanical characteristics of the structural adhesive.

[0027] With specific reference to FIGS. 3a-3 b, it can be seen that the joint has a transverse cross section thickness (t) at the joint. Though larger section thicknesses may be used and remain within the scope of the present invention, in certain highly preferred embodiments, the section thickness is less than about 7 mm, and still more preferably is less than about 5 mm (e.g., about 3 to about 4 mm). This further renders the present invention more advantageous than previous assemblies, which typically have employed larger section thicknesses.

[0028] Another advantage of the present invention is that, as shown in FIGS. 4a, 4 b, and 4 c, the heat exchanger, overall radiator assembly or both need not be rectangular. For instance, FIG. 4a shows the use of arcuate end tank to heat exchanger interfaces 42, with a heat exchanger 44 that includes a prominent rounded shape (e.g., circular, elliptical, oval or the like) edge configuration 46. They may include a plurality of different shapes. As illustrated in FIG. 4b, the sides of another heat exchanger 48 may have a straight portion 50. Optionally the perimeter of the heat exchanger 48 may include variations in heights (e.g., peaks 52 and valleys 54 as illustrated in FIG. 4b). Another radiator 56 may include a heat exchanger that is contoured in the fore-aft direction of the vehicle and need not be planar, as with conventionally configured radiators, as shown in FIG. 4c. Combinations of some or all of the above alternatives may be employed as well.

[0029] Though the present invention has been described in the context of automotive vehicle engine radiators, the use of the invention is not intended to be limited thereby. Any apparatus employing a radiator subject to operating conditions milder than or comparable to those experienced by an automotive vehicle engine may employ the present technology.

[0030] In preparation of the present assembly, the adhesive is applied by contacting the adhesive in a conventional fashion with one or more mating surfaces to form a continuous bead or film. The adhesive may be coated, extruded brushed or the like onto the surface. The adhesive can be applied immediately before joining components or it can be applied in remote location from the location where the components are bonded together, or the engine. The preferred cure-on-demand adhesive is exposed to conditions such that it will cure and thereby bond the components together and form a seal between them. Such conditions can be applied prior to or after bringing components together for joining. It is well within the average level of skill in the art to determine which operation may be used to cure the adhesive and when it should be performed. In one embodiment the operation may be an operation that is inherent in the assembly or operation of an automotive vehicle.

[0031] In another embodiment the assembly may include an outer shell and an inner shell adapted such that the inner shall is located within the outer shell and there is an insulating gap between the two. The gap can be filled with a fluid, or a solid material, such as elastomeric material or foam material. In another embodiment the radiator assembly may have associated with one of its surfaces a sound attenuating material such as an elastomer or foam.

[0032] In another embodiment the assembly of the invention can include a coating or film on the exterior or interior which functions to improve the barrier properties of the radiator to hydrocarbons. Such a coating of film can reduce the fugitive hydrocarbon emission from an automotive vehicle. Any coating or film which prevents the transmission of hydrocarbons through the assembly may be used. A preferred coating is a carbon-silica based plasma deposited coating as described in U.S. Pat. No. 5,298,587; U.S. Pat. No. 5,320,875; U.S. Pat. No. 5,433,786 and U.S. Pat. No. 5,494,712 incorporated herein by reference.

[0033] The assembly of the present invention is capable of withstanding a temperature of about 163° C. (about 325° F.) for at least about 2500, and more preferably about 3000 hours and about 177° C. (about 350° F.)for at least about 75 and more preferably about 100 hours. The assembly exhibits substantially no detectable degradation in the presence of automotive vehicle fluids, such as brake fluid, windshield washer fluid, power steering fluid, engine coolant (standard and lifetime), engine oil (standard, synthetic and sour), gasoline, diesel fuel, ethanol, methanol, starter fluids or the like. The assembly also exhibits no detectable degradation due to exposure to environmentally encountered compounds such as calcium chloride, sodium chloride, exhaust gas (e.g. type) or the like. In a particularly preferred embodiment, the resulting tensile strength of the adhesive of the joint in the assembly is at least about 4000 psi (28 MPa), more preferably at least about 6500 psi (45 MPa), and still more preferably at least about 9000 psi (62 MPa). Further preferably the strength of the joint is greater than the strength of at least one, and preferably more than one, of the individual molded components.

[0034] Further preferably the strength of the joint is greater than the strength of at least one, and preferably more than one, of the individual molded components.

[0035] The technology of the present radiator assembly can be employed in combination with other adhesively bonded engine components, such as described in commonly owned co-pending application Ser. No. 09/766,792 (“Adhesively Bonded Valve Cover Cylinder Head Assembly”), application Ser. No. ______ (“Adhesively Bonded Engine Intake Manifold Assembly”) (filed contemporaneously herewith), hereby incorporated by reference.

[0036] In yet another embodiment, the present invention is employed in the manufacture of an engine throttle body. The throttle body includes at least one plastic component (of like type as the radiator end tank components) having a surface that is contacted with a structural adhesive of the present invention for bonding to another surface. The throttle body may be made from a metal or plastic for adhesive attachment to a metal or plastic intake manifold of a diesel or ordinary combustion engine, without the need for a fastener or gasket. 

What is claimed is:
 1. A radiator assembly, comprising: a) a first component having an associated first mating surface; b) a second molded plastic component having an associated second mating surface; c) an adhesive in contact with said first mating surface and said second mating surface for joining said first component and said second component to define a radiator assembly, wherein the resulting joint has a strength greater than the strength of said second molded plastic component.
 2. The assembly of claim 1 wherein said first mating surface and said second mating surface are generally nonplanar.
 3. The assembly of claim 1 wherein said first component and said second component is a blend of a polyamide and a syndiotactic polystyrene.
 4. The assembly of claim 1 wherein each of said first component and said second component is an injection molded filled plastic blend of nylon 6,6 and syndiotactic polystyrene.
 5. The assembly of claim 1 wherein said joint is substantially free of a sealing gasket.
 6. The assembly of claim 1 wherein said joint is substantially free of mechanical fasteners.
 7. The assembly of claim 1 wherein the transverse cross section thickness at said joint is less than about 7 mm.
 8. The assembly of claim 1 wherein the transverse cross section thickness at said joint is less than about 5 mm.
 9. The assembly of claim 1 wherein a primer contacts said adhesive.
 10. The assembly of claim 1 wherein substantially the entirety of the first and second mating surfaces in contact with said adhesive is capable of bonding thereto.
 11. An automotive vehicle radiator assembly, comprising: a) a first molded thermoplastic end tank having an associated first mating surface; b) a second molded thermoplastic end tank having an associated second mating surface; c) a heat exchanger having a first end and a second end, said ends adapted for opposingly receiving respectively each of said end tank and c) an epoxy adhesive in contact with said first mating surface and said second mating surface for joining said end tanks to said heat exchanger to define an automotive vehicle radiator.
 12. The assembly of claim 11 wherein said first mating surface and said second mating surface are generally nonplanar.
 13. The assembly of claim 11 wherein said first end tank and said second end tank are blends of polyamides and syndiotactic polystyrenes.
 14. The assembly of claim 11 wherein said first end tank and said second end tank are injection molded filled plastic blends of nylon and syndiotactic polystyrene.
 15. The assembly of claim 11 wherein said joint is substantially free of a sealing gasket.
 16. The assembly of claim 11 wherein said joint is substantially free of mechanical fasteners.
 17. The assembly of claim 11 wherein the transverse cross section thickness at said joint is less than about 7 mm.
 18. The assembly of claim 11 wherein said heat exchanger is nonrectangular.
 19. The assembly of claim 18 wherein said heat exchanger includes a rounded shape edge configuration.
 20. The assembly of claim 11 wherein said heat exchanger is contoured in the fore-aft direction of the vehicle.
 21. An automotive vehicle radiator assembly, comprising: a) a first plastic end tank component molded from the group selected from filled polyamide and filled polyamide/polystyrenic plastics, and having an associated first mating surface and an integrally formed first member; b) a heat exchanger having a second mating surface and an integrally formed second member for coating with said first member to form a mechanical joint between said end tank and said heat exchanger; and c) an epoxy adhesive in contact with said first mating surface and said second mating surface for joining said first molded thermoplastic component and said second molded thermoplastic component to define an automotive vehicle radiator, wherein said resulting joint has a lap shear strength of at least about 4000 psi (28 MPa).
 22. The assembly of claim 21 wherein said first mating surface and said second mating surface are generally nonplanar.
 23. The assembly of claim 21 wherein said first component and said second component are blends of polyamides and syndiotactic polystyrenes.
 24. The assembly of claim 21 wherein said first end tank and said second beat exchanger are injection molded filled plastic blends of nylon and syndiotactic polystyrene.
 25. The assembly of claim 21 wherein said joint is substantially free of a sealing gasket.
 26. The assembly of claim 21 wherein said joint is substantially free of mechanical fasteners.
 27. The assembly of claim 21 wherein the transverse cross section thickness at said joint is less than about 7 mm.
 28. The assembly of claim 21 wherein the transverse cross section thickness at said joint is less than about 5 mm.
 29. The assembly of claim 21 wherein a primer contacts said adhesive.
 30. The assembly of claim 21 wherein substantially the entirety of the first and second mating surfaces in contact with said adhesive is capable of bonding thereto.
 31. The assembly of claim 21, wherein said adhesive of said resulting joint between said end tank and said heat exchanger has a tensile strength of at least about 6500 psi (45 MPa).
 32. The assembly of claim 21, wherein said adhesive of said resulting joint between said end tank and said heat exchanger has a tensile strength of at least about 9000 psi (62 MPa).
 33. The assembly of claim 21, wherein said end tank matingly engages said heat exchanger so that said adhesive of said resulting joint has a tensile strength of at least about 9000 psi (62 MPa), said resulting joint has a transverse cross section thickness less than about 5 mm; said resulting joint is substantially free of a sealing gasket; and said joint is substantially free of folding tangs and mechanical fasteners.
 34. The assembly of claim 21 wherein said heat exchanger is nonrectangular.
 35. The assembly of claim 21 wherein said heat exchanger includes a rounded shape edge configuration.
 36. The assembly of claim 21 wherein said heat exchanger is contoured in the fore-aft direction of the vehicle.
 37. The assembly of claim 33 wherein said resulting joint includes a flange disposed in a groove.
 38. The assembly of claim 37, wherein said groove is defined by a wall having a tang for achieving a snap fit. 